<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    html {
      height: 100%;
    }
    body {
      height: 100%;
    }
    .box {
      background-color: pink;
      width: 50%;
      height: 50%;
    }
  </style>
</head>
<body>
  <div class="box">盒子</div>
  
</body>
</html>